Simultaneous penetration monitoring of oil component and active drug from fluorinated nanoemulsions.

In the field of dermal drug delivery, determining the penetration depth of actives is a standard procedure for the development of novel formulations. Regarding the vehicle components, respective penetration studies are rather scarce due to their often challenging analytics. However, an understanding of the interactions between drugs and additives during skin penetrating could help to develop promising drug delivery systems. Thus, the objective of the present study was to simultaneously monitor the skin penetration of the incorporated model drug diclofenac sodium and the semifluorinated oil perfluorohexyloctane (F6H8) from newly developed nanoemulsions. In vitro tape stripping studies were conducted and the tapes were analysed for their content of drug and additive in parallel by HPLC and 19F NMR. The penetration depth and total recovered amount of both substances of interest were successfully determined on each tape strip. The vehicle oil compound F6H8 itself showed a very small skin penetration, while the penetration of diclofenac sodium was consistently about 9- to 10-fold higher. Higher amounts of the oil content led to higher skin penetration of diclofenac sodium and slightly increased oil penetration; this effect might be explained by the increasing occlusion effect caused by increasing amounts of fluorinated oil.

Novel concentrated water-in-oil emulsions based on a non-ionic silicone surfactant: Appealing application properties and tuneable viscoelasticity.

Silicone excipients are non-irritating ingredients that are extensively used in topical formulations. In the present study, innovative water-in-oil emulsions with a high water content stabilised by a non-ionic silicone surfactant were developed. Effects of formulation composition on its properties and stability were investigated. It was possible to prepare highly stable emulsions with a water volume fraction of up to 80%. The emulsions exhibited desirable application properties such as non-sticky and cooling qualities. A dependency of the viscosity on the water fraction was found; this offers the opportunity to create emulsions with fine-tuned rheological properties. Furthermore, it could be shown in skin studies that the in vitro release of a hydrophilic model drug is influenced by the configuration of the oil phase. The penetration of the silicone surfactant and the other deployed additives was monitored using combined tape stripping and ATR-FTIR experiments, revealing that the compounds remain in the superficial layers of the stratum corneum, thus minimising the risk for skin irritation.